Various types of trenchers have been developed for digging trenches for pipe lines, communications lines, and the like. Existing trenchers commonly include a looped chain type digging mechanism having a plurality of buckets that move the soil upwardly out of the trench during the digging process. Such trenchers may include a chain drive arrangement that transfers power from the trencher""s engine to the digging chain and buckets. However, such chain drives are prone to breakage, and have limited capacity for transferring power. Further, known trenchers of this type are relatively small, and are thus limited to relatively shallow trenches.
Another prior art trencher arrangement includes a mobile, powered base including a boom assembly. The boom assembly includes a first boom member pivotally mounted to the powered base, and a second boom member pivotally mounted to the opposite end of the first boom. A digging chain is looped along the second boom, and a drive shaft transfers power to the digging chain via a ninety degree drive positioned adjacent the pivotal interconnection of the first and second booms. In use, the first boom is rotated downwardly to a position approximately parallel to the ground surface, and the second boom and chain are oriented approximately vertical. To transport the trencher, the first boom is rotated upwardly to about a forty-five degree angle, and the second boom is rotated upwardly about the pivotal connection to the first boom to raise the digging chain above the ground surface, thereby permitting movement of the mobile base. However, the drive shaft interconnecting the powered base and the ninety degree drive unit has a single universal joint at each end. Because the universal joints are only operable within a relatively small angular range of motion, the upward rotation of the first boom relative to the powered base is limited. Further, in this type of trencher the ninety degree drive unit rotates with the second boom, such that the universal joint connecting the ninety degree drive unit to the drive shaft is placed at an angle when the second boom is rotated upwardly for transport of the trencher. The range of allowable rotation of the first boom relative to the powered base is limited, as is the rotation of the second boom relative to the first boom such that the overall length of the second boom is necessarily quite short to permit movement of the digging chain above the level of the soil surface for transport. These limited rotational ranges, and the relatively short second boom and digging chain necessarily limits this type of trencher to a relatively shallow trenching capability.
Another example of a shaft driven trencher is disclosed in Dondi U.S. Pat. No. 4,682,427. The Dondi trencher includes a laterally-extending boom mounted on a tractor. A wheel and disc are rotationally mounted adjacent the end of the boom for digging a trench. However, the Dondi trencher also has limited capability.
Accordingly, there existed a need for a durable trencher capable of digging deep trenches at a high digging rate.
One aspect of the present invention is to provide a shaft driven trencher including a mobile powered base, a boom assembly, a chain digging assembly, a drive assembly and a linkage. The boom assembly includes a first boom member pivotally mounted to the base at a first pivot and a second boom member pivotally mounted to the first boom member. The chain digging assembly has a plurality of buckets. The drive assembly operably interconnects the mobile base and the chain digging assembly, with the drive assembly including a drive shaft connected to the mobile base for powered rotation of the drive shaft. The drive assembly further includes a right angle gear unit with input and output shafts, with the right angle gear unit being pivotally mounted to the boom assembly for rotation about the output shaft. The linkage interconnects the right angle gear unit with the base and pivots the right angle gear unit during rotation of the first boom member. The linkage also maintains the input shaft of the right angle gear unit facing the first pivot.
Another aspect of the present invention is to provide a shaft driven trencher including a mobile powered base, a boom assembly, a chain digging assembly, a drive shaft, a linkage and a pivot assembly. The boom assembly includes a first boom member pivotally mounted to the base at a first pivot and a second boom member pivotally mounted to the first boom member. The chain digging assembly has a plurality of buckets. The drive shaft includes a first drive segment and a second drive segment, with the first drive segment being connected to the second drive segment by a universal joint. The linkage rotates and supports the second drive segment. The pivot assembly is operably connected to the linkage and the first drive segment, with the pivot assembly including a pillow block operably connected to the linkage and the first drive segment. The pillow block rotates and supports the first drive segment. Furthermore, the universal joint is located between the pivot assembly and the member, thereby permitting greater elevation of the boom and reducing the angle of the universal joint.
Yet another aspect of the present invention is to provide a shaft driven trencher including a mobile powered base, a boom assembly, a chain digging assembly, a drive shaft, a right angle gear unit and a pivot and linkage assembly. The drive shaft includes a first drive segment connected to a second drive segment by a universal joint. The right angle gear unit includes input and output shafts, with the right angle gear unit pivotally mounted to the boom assembly of the shaft driven trencher for rotation about the output shaft. The right angle gear unit is also connected to the second drive segment whereby the second drive segment rotates the input and output shafts. The pivot and linkage assembly supports and rotates the drive shaft and the right angle gear unit, with the pivot and linkage assembly including a linkage operably coupled to the first drive segment, the second drive segment and the right angle gear unit. The pivot and linkage assembly includes a pillow block, an arm and a pair of arcuate tracks, with the pillow block being interconnected to the base and supporting the first drive segment. The pillow block also is configured to slide with the arcuate tracks. The arm is interconnected to the pillow block and the linkage. The linkage interconnects the right angle gear unit with the base, pivots the right angle gear unit during rotation of the first boom member and maintains the input shaft of the right angle gear unit facing the first pivot.
The shaft driven trencher is efficient in use, economical to manufacture, capable of a long life, and particularly suited for digging very deep trenches. These and other features, advantages and objects of the present invention will be further understood and appreciated by those skilled in the art by reference to the following specification, claims and appended drawings.